Hello All,

Getting a setup going. Everything appears to be working well, except the throttle.

Obviously, going straight into the Rx works just fine.

The ESC normally plays a startup tone, and then 3 beeps to let me know it's ready. It does this when going straight into the Rx.

If I jump the Rx into the "in" side of ardupilot.

And hook the ESC into channel 3 on "out" side.

I get the startup tone, but not the following three beeps.

Has anyone else experienced something like this?

I've quadruple checked the servo connections, and they're correct.

Any suggestions?

Thank you!

John C.

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Went back and touched up the solder joints. Took everything off the board since the MUX channels are pass-though.

Mux1 and 2 pass-through. 3 simply does not. See example.

Example Video

Do I need a new ArduPilot board?

John C.
Do you have a meter with a continuity beep to check for bad connections?
The meter should beep when touching:
Ch3 input to Mux pin 11
Ch3 output to Mux pin 9

Note input/output pin is the inner pin labeled S. The other two are power and ground.
Look at the dot on the upper left corner of the mux. That's Pin 1. All pin numbers run counter clockwise on chips, making 9 the lower right pin.
Thanks for the reply Jason!

Which dot (pin 1) do you mean, the one on the PCB, or the one on the chip?


If I start with the dot on the PCB, I get a reading bewteen Ch3 input (S) and 11.

I get no reading change (on ->|- continuity setting) between Ch3 output (S) and 9.

Where can I go from here? Thanks!

Check the continuity between the pins and these two pins on the mux.

Perfect diagram. My previous readings were to the wrong pins on the mux.

My multimeter does not have a tone, but when I put it in continuity mode, without the probes touching, the meter stays at 1.

On the measurements per the above diagram, the meter reads .008 on one and .012 on the other.

To me, that means that they are continuous, and I would hear a beep.

Where would you go from here? Again, thanks for the help everyone.

Try the resistance measured in Ohms. Look for a very low value. Touch the leads together - that low.
In to 11 and 9 to Out should both be very low. A bad solder joint will have a high resistance.
Wish I could help you more.
Yep, the above numbers (.008 and .012) are in the Ohm scale (set to continuity). Just double-checked them all. When I touch the two probe together, I get to .022 or so.

Is my only option a new board here?


John, It's possibe the mux chip could have been damaged be ESD. All is not lost. You could use chn. 4 by moving the wire from mux 3 to mux 4 and solder on the extra connectors. The Aurdupiolot doesn't read inputs 3 & 4, it's not wired. These channel's outputs are just switched from computer to receiver when going to man. mode. If it works, that would confirm the problem plus get you going right away.
Absolutely makes sense.

Is there a .h setting that I would need to change to let ArduPilot know that I want output 4 to be the throttle?

I'll take a look myself as well...


Ok, Mux4 will allow me to pass through the throttle control.

What do I need to change in the code to make sure Ardu Pilot knows to use Mux4 for the throttle?

Digging around, and I'd just be throwing darts at this point.


You shouldn't have to change a thing. The ArduPilot code doesn't know anything about the MUX--it's just outputting PWM on that wire you soldered. If the wire goes to Mux4, then that's where the signal will go.

BTW, it does indeed sound like one of the channels of the MUX got fried. Glad you were able to switch to a working one...

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